Method: Aws::DynamoDB::Types::UpdateItemInput#expression_attribute_names

Defined in:

lib/aws-sdk-dynamodb/types.rb

#expression_attribute_names ⇒ Hash<String,String>

One or more substitution tokens for attribute names in an expression. The following are some use cases for using ‘ExpressionAttributeNames`:

• To access an attribute whose name conflicts with a DynamoDB reserved word.

• To create a placeholder for repeating occurrences of an attribute name in an expression.

• To prevent special characters in an attribute name from being misinterpreted in an expression.

Use the **#** character in an expression to dereference an attribute name. For example, consider the following attribute name:

• ‘Percentile`

^

The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For the complete list of reserved words, see [Reserved Words] in the *Amazon DynamoDB Developer Guide*). To work around this, you could specify the following for ‘ExpressionAttributeNames`:

• ‘“#P”:“Percentile”`

^

You could then use this substitution in an expression, as in this example:

• ‘#P = :val`

^

<note markdown=“1”> Tokens that begin with the : character are *expression attribute values*, which are placeholders for the actual value at runtime.

</note>

For more information on expression attribute names, see [Accessing Item Attributes] in the *Amazon DynamoDB Developer Guide*.

[1]: docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html [2]: docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html

Returns:

• (Hash<String,String>)

# File 'lib/aws-sdk-dynamodb/types.rb', line 7929

class UpdateItemInput < Struct.new(
  :table_name,
  :key,
  :attribute_updates,
  :expected,
  :conditional_operator,
  :return_values,
  :return_consumed_capacity,
  :return_item_collection_metrics,
  :update_expression,
  :condition_expression,
  :expression_attribute_names,
  :expression_attribute_values)
  include Aws::Structure
end